Means for preventing overheating electric resistances.



E. GRUENFELDTA MEANS FOR PREVENTING OVERHEATING ELECTRIC RESlSTANCES.

APPLICATION FILED JAN- 6. 1913- Patented June 27, 1916.

2 SHEETS-SHEET I.

E. GRUENFELDI.

MEANS FOR PREVENTING OVERHEATING ELECTRIC RESISTANCES.

APPLICATION FILED JAN-6,1913. I.,188,647.

2 SHEETS-SHEET 2.

u -Minnow AQZA; A9634 Pafinted June 27, 1916.

' '13 MIL' can Burnt-Dr, or onnyistrfiin, 'omd,

AssiGNo n, Y new Assmmvmnrsgo' Knn' 'nfa L e'oiv ranY, or CLEVELAND, c1110, A CORPORATION OF,OHIO.- i

ivrnairsron rnnv'nn'riue ovitnnnarine ELECTRIC RESISTANCES.

To (till 5 0 hem it may concern Be knownthat I,

subject of the Emperor of Germany,residf ing (jlevelandi infthe county of Guyahoga,

and State of Ohi, ,j have invented certain "new and;usefullmprovementsin and Rel'atin Mleans for Pi venting Overheating Electric Resista-nces,

iiig' infthe, c rcuit, more particularly where a resist'ance'is lntrod'uced in the circuit.

For the purpose of i lustrating my invention I have herein selected to disclose one embodiment of it in providing against overheating of a resistance ordinarilylemployed at certain times in the circuit between a storage battery and an electric motor in a motor vehicle. Carelessiot thoughtless operators of the motor vehicle have been knbwn to apply the brakes withthe circuit closed through a resistance. Under such circumstances the resistancehas been known to become so highly heated by the current flowing through it as to set fire to the motor vehicle.

*Tlig'ure 1 is a side elevation of aresistance with my is .1 plan view of the same. Fig. 3 is an end elevation. Fig. t is a perspective view of a grid. Fig. 5 is a perspective view of an insulating tube detached. Fig. 6 is a perspective view of a binding post detached. Fig. 7 a diagram of the resistantcircuit.

In the drawings, lyrepresentsa series of metal resistance sections or grids. They may be of any suitable construction. They are shownarranged side by side in a series. For-illustration I have selected cast metal grids of the conformation shown in Fig' 4L. They are assembled on tubular sections 2 of suitable insulating material, such as mica.

The grids or sections may be spaced apart in any desired manner. Each is shown as having three enlarged portions, 1, 1, 1", each enlarged portion having an opening through it to receive one of the insulating tubes or cores 2. Between the adjoining enlargedportions of adjacent grids may be [placed metal washers 3 and, where the grids are. to be insulated each from the next adjacent one or ones, suitable insulatlng disks or washers .4: may be used, such as mica. disks.

Specification' of Let ters Patent.

E U. ,Glil'llthlllfll'iD'lf, a

j, portion a. Of which the, following ,are, drilled .at 4:

a specification" Z i0" the posts invention applied thereto. Fig. 2'

5' are binding posts or connectors for-[re- Those illustrated in the drawings are formed by bendinga piece of metal upon itself, :as v.showninl g. 6, so as tocomprlsea tubular and flat portions a. The latter.

to receive the insulating tubes 2. p 6 are screws for blnding the conductors in y are binding .to the binding posts 5, the purpose of these, however, being to properly support in the electrieal circuit -fuses which have relatively lown'iclting po nts. .Each of thebmdin-g posts'i carriesan inwardly turned tube: 86f

metal, preferably a good conductor of electricity. The inner ends of two alined tubes 8 are spaced apart to receive fuses 9. The fuses 9 have ends 9 arranged to be inserted in two alined tubes 8 and U-shaped extensions 9 disposed between adjacent resistance grids or sections.

The resistance sections, washers both metal and insulating, and the tubes or cores 2 may be held together in any suitable man ner. For this purpose I have shown a framework consisting of strips of metal 1i, forming a rectangle. One of these rectangles is arranged at each side of the resistance and together with the parts of the resistance they are held or bound together by bolts 12 which extend through the insulating tubes 2. For the purpose of supporting the resistance I have shown sections of metal '12 likewise held in place by the bolts 12.

"Each of the fuses 9 has a current carrying capacity in excess of any current which is to be passed through it. Each of the fuses also is formed of material. which besides being a conductor of electricity, has a relatively low? thermal melting point, so that should the' circuit be closed through the resistance, although the current flowing through the fuse be below the carrying capacity of the fuse but sufiicient to heat up the resistance, then,

when the heat generated in the resistance PatentedJuneZV,1916." .;jfjaii nmaonaieaJanuar e,1913.: Serial No. "140,401;

ceiving electrical conductors or wires whi'chi: convey current to and from the resistance.

posts similar in construction Fig. 7 is a diagram illustrating the circuit in the resistance shown. Assuming that the current enters at the binding post R it flows through the first grid then throu h the, fuse!) which may be, for example a 5 ampere fuse, then through the second grid to the third grid and thence fourth grid to the binding post R. If the circuit is closed between the binding post R and B, only one fuse, which we have assumed to be a 75 ampere fuse is in the circuit. In the event that heat generated in the grids due to the flow of current therethrough exceeds a predetermined temperature, that is, the temperature at which the fuse 9 will melt, the fuse will burn out.

The next fuse in the circuit may be for a larger capacity in amperes than the first fuse, say 100 amperes, when it alone is in the circuit its capacity will be suflicient to permit a hundred amperes to flow, nevertheless should the heat of the resistance grids between which this fuse is located exceed a predetermined degree, the fuse will burn out or melt and open the circuit because of the existence of such degree of heat.

I have used this invention extensively in electric motor vehicles in connection with a resistance employed between the storage battery and an electric motor and have found it entirely suitable for preventing the overheating of the resistance so as to set fire to the motor vehicle.

To those skilled in the art of making apparatus of the class described, many a terations in construction and widely differing embodiments and applications of my invention will suggest themselves, without dearting from the spirit and scope thereof. lily disclosures and the description herein are purely illustrative, and are not intended to be in any sense limiting.

What I claim is A resistance for anelectric circuit and a Se connected in electric circuit with said resistance, said fuse having a U-shaped section with its base disposed between sections of said resistance and constituted to be melted at a predetermined temperature due to heat generated in said resistance by current flowing 'therethrough lower in value than the electrical carrying capacity of the fuse.

In testimony whereof I aflix my signature, in the presence of two witnesses.

EMIL GRUENFELDT. Witnesses:

Rosn HALL, EDWARD R. ALEXANDER, 

